Supplementary Table 1: The sentinel hospital IDs and locations. There are 23 hospital sites that perform laboratory confirmation of V. cholerae in Bangladesh.

ID Hospital Division Type
1 District Hospital Norshingdi Dhaka district
2 Adhunik Sadar Hospital Habiganj Sylhet district
3 District Sadar Hospital Cox’s Bazar Chittagong district
4 Adhunik Sadar Hospital Naogaon Rajshahi district
5 General Hospital Patuakhali Barisal tertiary
6 Adhunik Sadar Hospital Thakurgaon Rangpur district
7 District Sadar Hospital Satkhira Khulna district
8 Dhaka Medical College Dhaka Dhaka tertiary
9 Uttara Adhunik Medical College Hospital Dhaka tertiary
10 Bangladesh Institute of Tropical and Infectious Diseases Chittagong Chittagong tertiary
11 General Hospital Tangail Dhaka district
12 General Hospital Narayanganj Dhaka district
13 Sadar Hospital Chuadanga Khulna district
14 General Hospital Meherpur Khulna district
15 General Hospital Comilla Chittagong district
16 Upazila Health Complex Chaugachha Jesssore Khulna subdistrict
17 General Hospital Kusthia Khulna district
18 Upazila Health Complex Madan Mymensingh subdistrict
19 Upazila Health Complex Chhatak Sunamganj Sylhet subdistrict
20 Upazila Health Complex Mathbariya Barisal subdistrict
21 Upazila Health Complex Bakerganj Barisal subdistrict
22 Health Complex Shibganj Rajshahi subdistrict
23 icddr,b Cholera Hospital Dhaka icddrb

Supplementary Table 2: Population living in the cholera surveillance zone.

Buffer (Subdistrict-District-Tertiary-icddr,b in km) Pop Proportion
10-20-30-30 50888584 0.3129697

Supplementary Figure 1: A. Median risk of V. cholerae seroincidence relative to a population-weighted mean by 5 km x 5 km grid cell. These relative risk estimates are bounded such that RRs above and below 2 and -2 were plotted as the values 2 and -2, respectively. The black marks indicate sentinel hospital locations. B. Median number of estimated V. cholerae infections per grid cell in the previous year. The black marks indicate sentinel hospital locations. These estimates were calculated as the product of the median seroincidence risk and 2015 WorldPop population estimate in each grid cell. The black marks indicate sentinel hospital locations.

Figure 1: Cholera greyspots. The 5 km x 5 km grid cells that are colored are cells covered in the cholera surveillance zone. The greyed out grid cells are areas not captured by the national cholera surveillance system in Bangladesh, where we have little information on clinical cases of cholera.

Figure 2: A. Cholera risk map as categorized by the risk of seroincidence relative to a population-weighted mean by 5 km x 5 km grid cell. The map illustrates grid cells of High-Considerate-Moderate risk and the which grid cells are captured by the cholera surveillance zone (10-20-30-30km for subdistrict, district, and tertiary care, and icddr,b hospitals), indicated by the transparent buffers. B. Cholera risk map as categorized by the estimated number of V. cholerae infections by 5 km x 5 km grid cell. The black marks indicate sentinel hospital locations and the transparent buffers overlayed represent the cholera surveillance zone.

Figure 3: A. Bar plot of the number of people (above x-axis) and number of infections (below x-axis) in the Bangladesh population and in the cholera surveillance zone living in high-considerable-moderate risk areas as defined by relative seroincidence risk and absolute number of infections risk measures. B. Bar plot of the percentage of the population (above x-axis) and percentage of infections (below x-axis) in Bangladesh and the cholera surveillance zone living in high-considerable-moderate risk areas using the relative seroincidence risk and absolute number of infections as measures of risk.

Supplementary Figure 3:

Supplementary Table 3: Population living in each risk category. The population living in high, moderate, and low risk areas according to relative seroincidence risk and absolute risk across Bangladesh. The risk categories are defined by the 25th and 75th percentiles of the relative risk or number of infections in each grid cell.

Risk Level Population Risk Measure
High 35885510 Relative Risk
Considerable 64914640 Relative Risk
Moderate 61798921 Relative Risk
High 89111436 Absolute Risk
Considerable 68300021 Absolute Risk
Moderate 5187614 Absolute Risk

Table 1: The population not captured in the surveillance greyspots (cholera surveillance zone).

Greyspot type Greyspot population Percent in greyspot
Surveillance greyspot 111,710,486 68.7
Here: Using boots sampling to estimate sentivity table values

Table 2: Part 1. Number and percent infections that may be captured in cholera surveillance zones. The percent infected represents the percentage of infected individuals captured within the cholera surveillance zone out of all infected individuals in Bangladesh. Part 2. Number and percent infections that may be captured in cholera surveillance zones, categorized by relative risk and absolute risk. The infections in surveillance zone represents the percentage of infected people in high-considerable-moderate risk grid cells among all infections within the cholera surveillance zone. The population in surveillance zone represents the percentage of people living in high-considerable-moderate risk grid cells among all people within the cholera surveillance zone. The distribution should across risk categories should sum to 100% for each set of buffer sizes. Part 3. Number and percent infections that may be captured in Bangladesh, categorized by relative risk and absolute risk. The captured at-risk population represents the percentage of high-moderate-low risk populations captured by the cholera surveillance zone out of all high-considerable-moderate risk populations in Bangladesh. The captured infections represents the percentage of infections in high-moderate-low risk grid cells among all infections in high-considerable-moderate risk grid cells across Bangladesh.

Buffer size Surv. zone pop Number infected % infected in surv. zone pop % of all BGD infections
10-20-30-30km 50888584 8,005,303 ( 4,588,667 , 11,886,760 ) 15.7322 ( 13.3 , 23.4 ) 28.5276 ( 26.6 , 34.6025 )
Buffer size Risk Measure Risk category Number infected % surv. zone infections Surv. zone pop % BGD pop in surv. zone
10-20-30-30km Absolute Risk High 6,161,714 ( 3,464,602 , 9,159,009 ) 76.9664 ( 74.2 , 85.9 ) 32,815,402 ( 27,464,930 , 36,813,855 ) 64.4848 ( 61.6 , 72.3025 )
10-20-30-30km Absolute Risk Considerable 1,781,751 ( 758,604.3 , 2,775,329 ) 22.262 ( 19.6 , 30.6 ) 16,540,234 ( 13,284,654 , 20,448,577 ) 32.5042 ( 29.8 , 40.2025 )
10-20-30-30km Absolute Risk Moderate 61,838.36 ( 21,388.8 , 114,633.3 ) .7709 ( .6 , 1.3 ) 1,532,948 ( 537,929.3 , 3,589,343 ) 3.0118 ( 1.9 , 7.1 )
10-20-30-30km Relative Risk High 3,434,680 ( 1,800,494 , 6,016,285 ) 43.3947 ( 36.5 , 65 ) 10,060,550 ( 5,614,175 , 16,447,115 ) 19.7712 ( 16 , 32.3025 )
10-20-30-30km Relative Risk Considerable 3,583,606 ( 1,602,120 , 6,026,203 ) 44.4108 ( 39.4 , 58.5 ) 23,900,262 ( 16,973,965 , 31,466,839 ) 46.966 ( 41.275 , 61.8 )
10-20-30-30km Relative Risk Moderate 987,017.5 ( 218,968.8 , 2,435,070 ) 12.1946 ( 7.975 , 26.4025 ) 16,927,772 ( 8,459,092 , 26,323,286 ) 33.264 ( 26.4 , 51.7025 )
Buffer size Risk Measure Risk category Surv. zone pop Surv. zone infections Captured At-Risk Pop (%) Captured Infections (%)
10-20-30-30km Absolute Risk High 32,815,402 ( 27,464,929 , 36,813,855 ) 6,161,714 ( 3,464,601 , 9,159,009 ) 41.8975 ( 40.6 , 45.8025 ) 33.3241 ( 30.1 , 42.3025 )
10-20-30-30km Absolute Risk Considerable 16,540,234 ( 13,284,654 , 20,448,578 ) 1,781,751 ( 758,604.4 , 2,775,329 ) 22.025 ( 20.5 , 26.5025 ) 19.8105 ( 19 , 22.1 )
10-20-30-30km Absolute Risk Moderate 1,532,948 ( 537,929.5 , 3,589,343 ) 61,838.36 ( 21,388.71 , 114,633.8 ) 15.7958 ( 11.5 , 27.8025 ) 10.7625 ( 9.1 , 15.5025 )
10-20-30-30km Relative Risk High 10,060,550 ( 5,614,175 , 16,447,115 ) 3,434,680 ( 1,800,494 , 6,016,284 ) 26.3327 ( 22.4 , 38.1025 ) 25.8756 ( 21.6 , 39.0025 )
10-20-30-30km Relative Risk Considerable 23,900,262 ( 16,973,965 , 31,466,840 ) 3,583,606 ( 1,602,120 , 6,026,202 ) 30.0859 ( 27.5 , 36.7 ) 29.6678 ( 27 , 36.8 )
10-20-30-30km Relative Risk Moderate 16,927,772 ( 8,459,092 , 26,323,286 ) 987,017.5 ( 218,968.5 , 2,435,070 ) 36.5226 ( 31.875 , 49.0025 ) 35.6702 ( 31.6 , 47 )